[Characterization of the pathology of lactating cows based on the level of lactation. Principal factors in the variation and typing of pathologic profiles of lactation].

The health disturbances investigated were observed during a long-term trial (six years) conducted at an experimental station located at 1,100 m elevation. The study dealt with 487 lactations involving 190 cows of the Montbéliarde and French Friesian breeds, which produced on average 4,200 kg milk per lactation. The disturbances concerned 59% of monitored lactations, with a mean incidence of 2.1 disturbances per lactation. Lameness and mastitis accounted respectively for 52 and 24% of the clinical affections. Pathology was significantly influenced by breed, basic diet (hay or grass silage), concentrate quantities, lactation rank and year. The authors describe a method permitting an independent analysis of the effects of lactation stage and of season on mastitis and lameness frequency, by limiting the biases due to grouping of calvings and to culling. The study of lactations affected by several pathological disturbances shows that the different types of affections recorded are mutually independent but that successive occurrences of the same affection are not. On the basis of these results, the authors have proposed to globally characterize the "pathological profiles" of lactations.